This invention relates generally to an electrophotographic printing machine, and more particularly concerns a waste developer bottle for collecting and disposing of waste developer.
In the process of electrophotographic printing, a charge-retentive surface, also known as a photoreceptor, is charged to a substantially uniform potential, so as to sensitize the surface of the photoreceptor. The charged portion of the photoconductive surface is exposed to a light image of an original document being reproduced, or else a scanned laser image created by the action of digital image data acting on a laser source. The scanning or exposing step records an electrostatic latent image on the photoreceptor corresponding to the informational areas in the document to be printed or copied. After the latent image is recorded on the photoreceptor, the latent image is developed by causing toner particles to adhere electrostatically to the charged areas forming the latent image. This developed image on the photoreceptor is subsequently transferred to a sheet on which the desired image is to be printed. Finally, the toner on the sheet is heated to permanently fuse the toner image to the sheet.
One familiar type of development of an electrostatic image is called xe2x80x9ctwo-component development.xe2x80x9d Two-component developer material largely comprises toner particles interspersed with carrier particles. The carrier particles are magnetically attractable, and the toner particles are caused to adhere triboelectrically to the carrier particles. This two-component developer can be conveyed, by means such as a xe2x80x9cmagnetic roll,xe2x80x9d to the electrostatic latent image, where toner particles become detached from the carrier particles and adhere to the electrostatic latent image.
Despite the practical advantages of two-component development, which has caused this type of development to become very common in printers and copiers available today, a common problem involving two-component development relates to the degradation of two-component developer material over the life of a printer or copier. One print quality problem results from the fact that, as the toner in developer material is gradually consumed by being placed on the photoreceptor, and then from the photoreceptor onto print sheets, a constant quantity of carrier particles remains in the system. Over time, the ratio of toner to carrier particles in the developer mixture drifts from an optimal level. Further, the frequency of print quality defects tends to increase with the increasing length of service of a two-component development system. Such print quality defects may be caused by dirt generation from developer material that is nearing the end of its useful life. At service calls, however, developer material is frequently changed without knowing the condition thereof, often resulting in wasteful discarding of developer material that is still of satisfactory quality.
U.S. Pat. No. 4,614,165, assigned to the assignee hereof and incorporated by reference herein, discloses the general principle of what is known familiarly as xe2x80x9ctricklexe2x80x9d development. Very briefly, trickle development involves providing two distinct supplies of developer: a main supply, from which the development unit draws developer for application to the electrostatic latent image, and a second, separate developer supply which is used to replenish the first supply over time. Typically, the two quantities of developer have substantially different ratios of toner to carrier. In the embodiment described in the ""165 patent, for example, the first developer supply in the housing of the development unit is 96% carrier by weight and 4% toner by weight, while the developer material being gradually dispensed into the first supply is 25% carrier by weight and 75% toner by weight. Over the course of the lifetime of the printer, or at least of the development unit, the relatively toner-rich developer in the second supply is gradually discharged, or caused to xe2x80x9ctrickle,xe2x80x9d into the first developer supply. This trickling provides a substantially continuous replenishment of toner rich developer, and thereby maintains the effective ratio of toner to carrier within the main developer supply within an optimal range for a longer period of time. This trickling thereby extending the useful life and the optimal print quality associated with the development unit.
In a trickle development system, as a fresh supply of developer is discharged into the housing of the development unit, it is typically necessary that a similar quantity of surplus developer be discharged from the housing of the development unit. This surplus or xe2x80x9cwastexe2x80x9d material is commonly collected in a waste bottle. An auger contained in a transport tube is often used to transport the waste material through the tube to the waste bottle. The transport tube, with the auger therein, typically extends through a seal in an opening in the waste bottle. Waste material traveling through the transport tube is discharged into the waste bottle through an opening in the tube.
When the waste bottle becomes filled with waste developer, it is necessary to remove the full bottle and replace it with an empty bottle. The bottle is removed from the development unit by sliding the bottle off the end of the transport tube. If the waste bottle is filled to the top with developer, waste developer in the bottle is dragged by the auger vanes, which are exposed through the opening in the transport tube, and by the edges of the opening in the tube through the seal in the bottle. When the opening in the transport tube clears the seal, the developer that has been dragged through the seal falls from the auger and the transport tube into the machine. As a result, the interior of the machine becomes soiled with developer.
There is a need in the art for a toner waste bottle that can be removed from the waste auger without developer being dragged through the seal and soiling the machine.
One form of the invention provides a container for collecting waste developer discharged from a developer module through a waste developer discharge conduit, comprising: a housing defining a chamber including a partition wall dividing the chamber into a collection chamber and an overflow chamber, said housing having an opening formed in the region of the overflow chamber to receive said discharge conduit therethrough, said discharge conduit extending through said overflow chamber, over an inner edge of said partition wall and into said collection chamber, so that waste developer is discharged into said collection chamber.
Another form of the invention provides an electrostatographic reproduction machine comprising: a developer module having a discharge conduit extending therefrom for discharging waste developer from said developer module; a waste collection bottle enclosing a chamber including a partition wall separating said chamber into a collection chamber and an overflow chamber, said bottle having an inlet opening in the region of said overflow chamber, said discharge conduit extending through said inlet opening, through said overflow chamber, over an inner edge of said partition wall and into said collection chamber, such that said waste developer is discharged into said collection chamber.